Vladimir Putin has come under fire for lining up "combat dolphins" to act as "guard dogs" in his war in Ukraine.

Satellite images taken earlier this week revealed the marine animals are being kept in sea pens close to where Ukrainian special forces have made incursions near the Crimean peninsula, the Daily Star previously reported. "The dolphin deployment to Novoozerne – with Putin putting them in harm’s way – may indicate they are seen as militarily useful," an unnamed source said.

But the decision to prep the creatures for war has attracted criticism, with animal rights group PETA dubbing the dolphins "cannon fodder". The group's Vice President of Programmes, Elisa Allen, told the Daily Star: "Animals don’t wage wars, and to use them as involuntary cannon fodder is despicable.

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The comments follow the news Putin is moving his fleet of dolphins closer to the front line
The comments follow news Putin is moving his fleet of dolphins closer to the front line (stock)

"In this case, these free-living marine mammals would have been trained to go against their very nature and denied basic sustenance so that trainers could force them to plant bombs, attack humans, and perform other destructive acts. It’s reprehensible for Putin or any other warmonger to subject animals to dangerous and cruel missions in a conflict they never enlisted in."

Russia's use of dolphins in war dates back to the 20th century. The nation's underwater army doubled in size earlier this year as the war with Ukraine rages on, with the creatures having been trained at the country's Sevastopol naval base in Crimea.

Russia also doubled it's troop of military-trained dolphins this year
Russia doubled its troop of military-trained dolphins this year (stock)

Russia isn't the only country training dolphins for underwater military missions such as detecting mines and to act as underwater "guard dogs" to warn about potential attacks. The idea was first adopted by the US and Swedish navies in the early 1960s, but was soon picked up by the Soviet Union.

Following the collapse of the towards the end of the 20th century, the entire Soviet combat dolphin programme was handed over to Ukraine but after the annexation of Crimea in 2014 the main base for the dolphins was once again in Russian hands.

Russia is not the only country to have trained the animal to detect mines and lost equipment on the sea bed, and to guard against underwater attack
Russia is not the only country to have trained dolphins for combat (stock)

The Russian navy is known to have bought a number of additional bottlenose dolphins in 2016. Evidence obtained by Naval News shows that the number of dolphin pens at Sevastopol has increased from four to seven in recent months.

Novoozerne is a former Soviet submarine base where Russia has deployed missile corvettes, landing craft and some support vessels including a submarine support ship. It now also plays host to the army of dolphins, according to reports.

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